1. Field of the Invention
This invention relates to an automatic guidance system for a flight vehicle having a parafoil and a navigation guidance apparatus for the system.
2. Description of the Related Art
Dropping of cargoes, weather observation, recovery of unmanned flight vehicles and spacecraft using parachutes such as ram-air parachutes, parafoils and the like, have often been made because they can be made on even the unlevelled ground other than runways.
However, dropping and recovery of cargoes by means of flight vehicles having parafoils tend to be affected by wind and as the actual descent position may be deviated from a target descent position, the flight vehicle has been guided in the direction of correcting the deviation by steering the para foil.
JP-A 5-185993, for example, describes such a guidance apparatus as the related art for guiding purposes.
The guidance apparatus as disclosed in JP-A 5-185993 is, as shown in a block diagram of FIG. 14, used to judge the present traveling direction of a gliding flight vehicle using a controller 103 from the three-dimensional positions (X, Y and Z) of the flight vehicle detected by a GPS 101 and the horizontal directions (Bx and By) thereof detected by a geomagnetic sensor 102. Then a drive signal (xc2x1V) is sent to a DC motor 104 in answer to the deviation of its traveling direction from the direction of a preset target descent position whereby to make the flight vehicle turn so that the traveling direction may conform to the direction of the target descent position by operating the left or right control line 105 of a para foil corresponding to the direction of correcting the deviation.
In this guidance apparatus, position and attitude detections are respectively made by the GPS 101 and the geomagnetic sensor 102 at all times even when a flight vehicle P receives lateral wind W while the flight vehicle having a parafoil is traveling toward a target descent position O. Thus, the guidance apparatus keeps controlling the flight vehicle so as to direct its traveling direction toward the target descent position as shown by an arrow E by quickly correcting its attitude and course even though the flight vehicle is on the course of receiving the lateral wind as shown by a solid line in FIG. 15.
According to JP-A 5-185993, the course of the flight vehicle can be corrected by correcting its position and attitude at all times and even when the influence of the wind is exerted upon the flight vehicle, its attitude can be corrected quickly.
Since the guidance is given in only correcting the traveling direction to the direction of the target descent position, there is fear that accuracy of descent will be lowered considerably under the influence of moderate gale. Accordingly, the selection of a flight path is important because such a flight vehicle as is equipped with a para foil is unable to recover its altitude.
The present invention is intended to obviate the aforesaid problem of the related art and it is object of the present to provide an automatic guidance system for a flight vehicle having a parafoil and a navigation guidance apparatus for the system designed to secure a proper flight path and make greater accuracy of descent available.
In order to accomplish the object above, the invention of an automatic guidance system for a flight vehicle having a parafoil is such that the system for guiding the flight vehicle having the parafoil to a target grounding point, the system comprises the steps of: opening the parafoil of the flight vehicle dropped in a predetermined area above a grounding target point; estimating wind velocity and wind direction after the parafoil of the flight vehicle is opened; determining the landing flight path of the flight vehicle based on the estimated wind velocity and wind direction; guiding the flight of the flight vehicle to the determined landing flight path; and making the flight vehicle descend according to the landing flight path.
Further, the invention of a navigation guidance apparatus for a flight vehicle having a parafoil is such that the apparatus for guiding the flight vehicle having the parafoil to a target grounding point, the apparatus comprises wind-velocity and wind-direction estimating means for estimating wind velocity and wind direction after the parafoil of the flight vehicle is opened; land flight path determining means for determining the landing flight path of the flight vehicle based on the wind velocity and wind direction estimated by the wind-velocity and wind-direction estimating means; and flight control means for controlling the parafoil so that the flight vehicle descends according to a landing flight path determined by the flight path determining means.